Air cushion vehicle with retractable skirt assembly

ABSTRACT

An air cushion vehicle has a body in which a peripheral skirt assembly is retractable from an operative position, in which the skirt assembly surrounds a space below the bottom of the body, to a retracted position in which the body side surfaces are exposed substantially to the body gunwale. The skirt assembly is provided as a plurality of skirt sections. The skirt assembly is arranged so that the hover height of the vehicle may be increased by movement of the skirt sections through the initial portion of their movement from their deployed positions to their retracted positions.

United States Patent 11 1 Anders et al. 1 Dec. 4 1973 AIR CUSHIONVEHICLE WITH 3,550,718 12 1970 Knuth et al. 180/127 x RETRACTABLE SKIRTASSEMBLY FOREIGN PATENTS OR APPLICATIONS 1 Inventors: Edward Anders,Houston; Lloyd 1,140,563 1/1969 Great Britain: 180/116 G. Nichols,Missouri City, both of I Primary ExaminerRichard A. Schacher [73]Assignee: Global Marine Inc., Los Angeles, Assistant Exa miner GeneChurch Cant AtzorneyRobert L. Parker et al.

[22] Filed: July 7, 19'72 [57] ABSTRACT PP N03 269,858 An air cushionvehicle has a body in which a peripheral skir t assembly is retractablefrom an operative po- 52] US. Cl. 180/127 Shim, which the assemhliySurrounds a Space 51 Int. (:1. B60r 1/16 below the of the a retractedPosition [58] Field or Search 180/116-130; in which the Side surfacesare exposed Substan- I 104/23 FS; 115/67 tially to the body gunwale. Theskirt assembly is provided as a plurality of skirt sections. The skirtassem- [56] References Cited bly is arranged so that the hover height ofthe vehicle may be increased by movement of the skirt sections UNITEDSTATES PATENTS through the initial portion of their movement from3,387,685 6/1968. Fresh et al. 180/119 their deployed positions to theirretracted position, 3,481,423 12/1969 Winter 180/117 3,483,939 12/1969Maddock et 180/127 20 Claims, 6 Drawing Figures oooo 'ononoo PATENTEDDEC 4 i915 sum 3 m 3 F/EE F/LiE AIR CUSHION VEHICLE WITH RETRACTABLESKIRT ASSEMBLY BACKGROUND OF THE INVENTION the copending application,the vehicle body is pro-- vided in the form of a barge-like floatablestructure having a flat bottom and side surfaces. A drilling rig, an oilor gas production'facility, or some other desired facility may bemounted to the body. The vehicle is useful on land, in water or iniceover water lo adapt the vehicle, when equipped with a drilling rig,forexample, for use in drilling an underwater well at an ice-coveredlocation, the vehicle body includes means for transferring energy, suchas thermal energy, through the side and bottom surfaces of the body.Thus, the body may be floated in a pool of water in an ice sheet duringdrilling operations, and may hold position within a moving ice sheetover a submerged well by melting its way into the ice; in effect thepool in which the vehicle floats is kept over a submerged location whilethe ice moves.

The vehicle of the copending application is movable over land, water orice in an aircushion mode. Therefore, the vehicle includes a peripheralskirt assembly and a system for supplying air at superatmosphericpressure to a space below the vehicle body bounded by the skirt assemblyso that the vehicle may be towed or self-propelled on a cushion of air.The skirt assembly is removably connected tothe body adjacent thegunwale of the barge-like body. Removability of the skirt is necessaryso that the side surfaces of the body may be exposed when the vehicle isused in ice as described above. The presence ofthe skirt assemblybetween the ice and the body side surfaces would impairthe effectivenessof the energy transfer means to function to hold the vehicle at a fixedposition relative to a moving ice sheet.

The skirt assemblies of air cushion vehicles conven- I tionally arefabricated of relatively heavy fabric impregnated with an elastomericmaterial tobe air impervious and wear resistant. Such skirt assembliesare heavy and difficult to handle in the best of circumstances, but incold weather, as in the arctic, they are considerably more difficult tohandle for connection and disconnection to the vehicle body. Emergenciesmay arise during the drilling of an oil well, or by reason of naturalevents in the arctic, which make it necessary for the vehicle of thecopending application to be removed quickly from its floating statewithin an ice sheet; such removal requires that the vehicle be operaircushion vehicles intended for use in the situations described above. Tobe effective, however, the skirt assembly must be retractable to aposition in which the vehicle side surfaces are fully exposed so thatthe energy transfer means described in the copending application may beused effectively.

Several retractable air cushion skirt arrangements have been describedin the prior art, but because of certain limitations and disadvantagespresent in each of them they do not provide a solution to the problemwhich has been identified above.

US. Pat. No. 3,321,039 describes a skirt assembly which is retractableto above the flat bottom of the body of an air cushion vehicle. Theretracted position of the skirt is outboard of the side surfaces of thebody. Thus, the use of this form of retractable skirt in the vehicle ofthe copending application would disable the energy transfer mechanismsprovided for the vehicle side surfaces. The retractable skirt assemblies'described in U.S. Pats. Nos. 3,387,685 and 3,550,718 suffer from thesame disadvantages and limitations.

US. Pat. No. 3,379,270 describes another retract able skirt arrangementin which a sponson extends radially outwardly of the vehicle body aroundthe gunwale of the body. The skirt assembly is connected adjacent theouter edge of the sponson and is retractable to engagement with thebottom surfaces of the sponson, thereby exposing the side surfaces ofthe body below the sponson. This arrangement is not suitable to overcomethe problem described above because of the use of the sponsons. Wherethe vehicle of the copending' application is used in ice, it is likelythat ice may rise above the gunwale of the vehicle body; a sponson atthe gunwale would engage such ice and prevent intimate cooperationbetween theenergy transfer mechanisms and the ice and thereby preventeffective use of the energy transfer mechanism for station-keeping ofthe vehicle in an ice sheet. 7

In view of the foregoing, therefore, a need exists for a retractableskirt assembly for an air cushion vehicle capable of being retracted toa position exposing the side surfaces of the vehicle body. Whenthe skirtis re tracted, the vehicle should present minimum structure projectingoutwardly beyond the body side surfaces.

SUMMARY or THE NvENTIoN This invention provides an improved. retractableskirt assembly for an air cushion vehicle. When the skirt assembly isretracted, the side surfaces of the vehicle body are exposed over theirentire area. Also, in the retracted position of the skirt, the vehicleprovides minimum structure projecting outwardly from the body sidesurfaces. a i

The present Skirt assembly preferably is arranged so that it may bepartially retracted and so that such partial retraction produces anincrease in the effective hover height of the vehicle body above anadjacent sup porting surface. Also, it is preferred that the skirtmaterial be furled in a retracted condition to obtain maximum protectionof the retracted'skiirt from damage and to minimize the volume occupiedby the retracted skirt.

The improved skirt is provided by structure which is rugged, simple,reliable and efficient, and which may be operated quickly to dispose theskirt in a deployed state for aircushion mode operation of the vehicle.The

skirt and its associated structure preferably are arranged for efficientuse in a vehicle of the type described in Patent No. 3,749,162 but itwill be recognized by Workers in the art of air cushion vehicles thatthe present invention may be used to advantage in other types of aircushion vehicles Generally speaking, this invention is provided in thecontext of an air cushion vehicle which includes a body having a gunwaleand side surfaces which extend downwardly from the gunwale to the bottomof the body. A flexible skirt is connected peripherally of the body andextends adjacent the body side surfaces for enclosing a space below thebody. Means are provided for supplying air at superatmospheric pressureto the space for supporting the body above an adjacent support surface.In this environment, the improvements provided by this inventioncomprise a plurality of skirt sections which are arranged to cooperatewith each other to define the skirt. Each skirt section is movablymounted to the bodyfor movement of the section from a deployed positionin which the .skirt sections cooperate with adjacent sections sodisposed to define the skirt and to enclose the space. The skirtsections are movable from this operative position to a second positionin which they are disposed substantially adjacent the gunwale and thebody side surfaces are exposed.

DESCRIPTION OF THE DRAWINGS The above-mentioned and other features ofthis invention are more fully set forth in the following detaileddescription of a presently preferred embodiment of the invention, whichdescription is presented with reference to the accompanying drawings,wherein:

FIG. 1 is a cross-sectional elevation view of an air cushion vehicle,operating in its air cushion mode, equipped with a retractable skirtaccording to this invention;

FIG. 2 is a top plan view, partially in cross-section, of the vehicleshown in FIG. 1;

FIG. 3 is an enlarged fragmentary crosssectional elevation view of aportion of the structure shown in FIG.

FIG. 4 is an elevation view taken along line 44 in FIG. 3;

FIG. 5 is an enlarged cross-section view taken along line 55 in FIG. 4;and

FIG. 6 is an enlarged cross-section view taken along line 6-6 in FIG. 4.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT As shown in FIG. 1, an aircushion vehicle 10 includes a body 11 which has a barge-likeconfiguration with a deck 12, a flat bottom 13, and side walls 14. Sidewalls 14 may have upwardly and outwardly sloping lower portions 15 andvertically disposed upper portions 16 which intersect deck 12 to definea gunwale 17 which extends around the perimeter of vehicle body 11. Itis within the scope of this invention, however, that side walls 14 ofthe vehicle body 11 may be entirely of the sloping type, exemplified bylower portions 15, or of the vertical type, exemplified by verticalsections 16; if the vehicle body is provided with vertical side walls,then it is preferred that the side walls be merged into the flat bottomsurface of the body by a rounded bilge, for example.

So that vehicle 10 may be used according to the disclosures of theabove-identified copending application, a plurality of energy transfermechanisms 19 are provided within the vehicle body in association withthe bottom and side wall surfaces of the body. By way of I example,energy transfer mechanisms 19 may be provided in the form of a pluralityof tubes 20 disposed in intimate engagement with the inner surfaces ofthe vehicle bottom and side walls and through which a heated heattransfer fluid may be circulated. Accordingly, when the vehicle sidewalls are exposed to the exterior of the vehicle and the vehicle body isdisposed in a pool of water formed in an ice sheet, heated fluid may becirculated through tubes 20 to maintain the water pool within the icesheet and also to melt the walls of the pool to enable the pool to staystationary over a submerged location even when the ice sheet moveslaterally relative to the submerged location.

In order that vehicle 10 may be operated in an air cushion mode forsupport of bottom 13 above an adjacent support surface 24, such asground or water or the top of an ice sheet, vehicle 10 includes an airpressurizing and circulation system. The air system includes a blower 25mounted to the deck of the vehicle body, for example. Blower 25 has aninlet 26 and an outlet duct 27 through which air is discharged atsuperatmospheric pressure. This pressurized air is supplied to a spacebelow bottom 13 which is enclosed by a skirt assembly 23 disposedcircumferentially of body 11. While pressurized air can be supplied tothe enclosed space in many ways, in vehicle 10 such supply is via aplenum structure 22. Plenum structure 22 has an operative positioncircumferentially of vehicle body .11 adjacent gunwale 17. Skirtassembly 23 is connected to the plenum structure to depend from theplenum structure to an operative position below the bottom 13 of thevehicle body, as shown in FIG. 1. As shown best in FIG. 2, a duct 28extends around the vehicle adjacent gunwale 17 and receives pressurizedair from blower- 25 via out let duct 27. The plenum structure 22 isconnected at selected locations around its extent to duct 28 viasuitable branch ducts 29. Blower 25 is operated by a diesel engine 30,for example. Accordingly, when blower 25 is driven by engine 30, itdischargesair at superatmospheric pressure to plenum structure 22 viaduct 28 and branch ducts 29. This pressurized air is applied via skirtassembly 23 to below the bottom 13 of the vehicle. The pressure of theair supplied to the skirt assembly is sufficient that the vehicle bodyrises above surface 24 by reason of the pressure of the air in a spacebetween vehicle bottom 13 and surface 24 bounded by skirt assembly 23.This is the hover or air cushion mode of operation of vehicle 10 and isillustrated in FIGS. 1 and As shown best in FIG. 2, it is preferred thatthe plan configuration of vehicle body 11 be substantially rectangular.Plenum structure 22 is defined by a plurality of plenum sections 33,there being at least one plenum section 33 provided for each of the foursides of the vehicle. FIG. 2 shows that at least two plenum sections 33may be provided for each of the sides of the vehicle and that a singleplenum section 33 may be provided across each end of the vehicle. Endplenum sections 33 are of sufficient length transversely of the vehicleto encompass the width of the vehicle and the width of the plenumsections 33 on opposite sides of the vehicle. Thus, when plenum sections33 and 33' are disposed in their operative deployed positions shown inFIG. 2, the plan configuration of the overall vehicle is substantiallyrectangular as shown in FIG. 2. Preferably, plenum sections 33 and 33'are arranged so that when they are in their deployed position there isno fluid flow communication directly between adjacent plenum sections.

As shown in FIGS. 2 and 3, each plenum section includes a top plate 34,an outer plate 35, an inner plate 36 and end plates 37. The top, outerand inner plates are rigidly interconnected and held in position bysuitable truss members 38 spaced along the length of the plenum section.The central portions of the truss members are open as at 39 (see FIG.3), to provide fluid flow communication within the length of each plenumsection. As shown best in FIG. 3, the bottom of each plenum section isopen in that no closure plate is con nected across truss members 33between the lower margins of outer and inner plates 35 and 36. A branchduct 29 is connected from duct 28 to each of plenum sections 33 throughthe top plate of the plenum section; because'the plenum sections aremovable, the branch ducts preferably are flexible and extensible so thatair flow communication from duct 28 to the plenum sections is maintainedthroughout the full range of movement of the plenum sections. Thus, theinterior of each plenum section communicates through its bottom to theinterior of a corresponding skirt section 40 which is connected at itsupper extent to the plenum section.

Each skirt section 40 includes an inner sheet 41, an outer sheet 42, andopposite end sheets 43, each of which is connected at its upper marginto those surfaces of the corresponding plates of the plenum sectionwhich open to the interior of the plenum section. Thus, each plenumsection functions as a support structure for the corresponding skirtsection. For example, inner sheet 41 of skirt section 40 is connected tothe surface of plenum section inner plate 36 which opens toward theinterior of the plenum section, as shown in FIG. 3. A-plurality ofpartition webs 44 are spaced along the length of each skirt section andare interconnected between the inner and outer sheets of the skirtsection. Each partition web 44 has an upper edge 45 which preferably isspaced below the plenum section but which, in a preferred form of theinvention, intersects the inner sheet adjacent the connection of theinner sheet to plate 36 of the adjacent plenum section. Each partitionweb has a lower edge 46 which intersects the lower edges47 and 48 of theskirt section inner and outer sheets, respectively. Partition webs 44are provided within the'skirt sections to assure that the inner andouter sheets of the skirt section are disposed in a predeterminedrelationship to each other when air is supplied to the skirt sectionsduring air cushion mode operation of vehicle 10. It is preferred thatthe lower edge 47 of inner sheet 41, during air cushion mode operationof the vehicle, be disposed adjacent the turn of the bilge 21 of body 11inwardly of and above the operative position of the lower edge 48 of theouter sheet.

At least the outer and end sheets of each skirt section are airimpervious and it is preferred that the inner plate and the deck of thevehicle at gunwale 17. It is sheet of each skirt assembly also be airimpervious. The

hinged to vehicle body 11, as by a pair of hinge assemblies 50 spacedalong the length of each plenum section and interconnected between theplenum section top preferred that the hinge axis 51' for each plenumsection be located just outboard of the gunwale, as shown in FIG. 3, orat the gunwale line. A retracting mecha nism 52 is interconnectedbetween the vehicle body and each plenum section for moving the plenumsec tion about hinge axis 51 between an operative deployed position,shown in solid lines in FIG. 3, and a retracted position, shown inbroken lines in FIG. 3. When the plenum sections are in their deployedposition, the top plates of the several plenum sections are essentiallycoplanar with deck 12 of vehicle 10, and theinner plates 36 of eachplenum section abut and are supported by the outer walls of vehicle body11. In their retracted positions, the plenum sections are disposed sothat their top plates are disposed at least vertically as shown in FIG.3, or preferably, are sloped inwardly toward the center of vehicle 10from adjacent hinge axes 51. An

optimum disposition of the plenum assemblies in their other, when air issupplied at superatrnospheric pressure to the skirt sections, to causethe end sheets and inner sheets of. the several skirt sections to abuteach other and effectively seal off the lateral boundaries of the spaceprovided below the vehicle body. In effect, then, plenum sections 33 and33' and the skirt sections carried by them cooperate, when the plenumsections are in their fully deployed position, to function as a unitaryplenum structure and skirt extending circumferen tially of vehicle body11.

The retraction mechanism 52 provided for each plenum section mayconveniently include a double-acting hydraulic or pneumatic ram assembly53 pivoted, as at 54 and 55, to a suitable bracket 56 connected to theplenum section top plate and to vehicle deck 12, respectively.

To further assure that the side walls of vehicle body 11 will be exposedto the maximum extent possible when plenum sections 33 are disposed intheir retracted positions, vehicle 10 includes means for furling skirtsections 40 relative to each corresponding plenum section. The furledstate of the .skirt sections is indicated in FIG. 3 at 60, shown inbroken lines. The furling mechanism for each skirt section includes aplural ity of draw lines 61, only one of which is shown in FIG. 3. Adraw line is provided at each, of a plurality of stations along thelength of the skirt section. Each draw line is connected at its outerend62 via a suitable connector 67 to a tie-down bar 70 secured to theinner face of inner skirt sheet 41 adjacent its lower edge 47. From thisconnection, each draw line extends across the interior of the skirtassembly, parallel to the plane of partition webs 44, through an opening63 provided in the outer sheet adjacent its lower edge 48. Openings 63preferably are of small diameter to minimize leakage of air from theinterior of the skirt through the openings during air cushion modeoperation of the vehicle. Each opening 63 may be defined by a grommetlocated in the skirt outer sheet and having an inner diameter somewhatlarger than the diameter of draw line 62. After passing through opening63, each draw line 61 extends upwardly along the outer face of outersheet 42 through a plurality of spaced guide eyes 64 which are affixedat appropriate locations to the outer sheet. Each draw line is passedover a suitable rotatable guide roller 65 mounted to the plenum sectionat the upper outer corner of the plenum section defined by the jointbetween the top and outer plates of the plenum section. Each draw lineextends from roller 65 via suitable additional guide rollers (not shown)to a winch mechanism 66. which is illustrated to be mounted to deck 12,but which may be mounted in any convenient location within the structureof the vehicle. If desired, all of the draw lines for a given skirtsection may be led to a com-, mon winch or to individual winches.

It will be apparent that, because of the arrangement of the draw linesrelative to the inner and outer sheets of each skirt section, reeling inof the draw lines after the adjacent plenum section has been moved toits retracted position will cause the skirt assembly to be rolled upupon itself to a furled It will be apparent that, because of thearrangement of the draw lines relative to the inner and outer sheets ofeach skirt section, reeling in of the draw lines after the adjacentplenum section has been moved to its retracted position will cause theskirt assembly to be rolled up upon itself to a furled storage stateindicated at 60 in FIG. 3. Furling of the skirt sections is facilitatedby making the skirt sections as flexible as possible, and it is for thisreason that it is preferred that partition webs 44 be defined by afabric which has not been increased in thickness or stiffness by beingimpregnated with an elastomeric material or the like to render itimpervious to the passage of air.

Assume that plenum sections 33 and 33 are in their retracted state andthe skirt sections are furled as indicated in FIG. 3. If it is thendesired to move the plenum sections to their operative deployed positionand to commence air cushion mode operation of the vehicle, retractionmechanisms 52 are operated to move plenum sections to their deployedpositions. Air is then applied to the interior of the plenum sectionsfrom blower 25. The application of pressurized air to the interior ofthe plenum section acts upon the furled skirt sections to bias the skirtsections from the furled state to their fully deployed state shown inFIG. 3. Accordingly, draw lines 61 are paid out from winches 66 topermit the skirt sections to unfurl. Control over the rate at which thedraw lines are paid out provides control over the rate of unfurling ofthe skirt assemblies.

An inspection of FIG. 1 will show that during air cushion mode operationof vehicle 10, it is necessary to constrain inner sheets 41 of skirtassembly 23, at locations on the inner skirt sheets near the bilge 21 ofvehicle body 11, from moving outwardly relative to the vehicle body. Thelack of such constraint upon the skirt sections during air cushionoperation will result in the skirt sections being blown outwardlyrelative to the vehicle body about the connection of the several skirtsections to plenum sections 33. Such a blow out is produced by virtue ofthe superatmospheric pressure provided within the space bounded by theskirt assembly as blower 25 is operated.

' Tie-down bars 70, one of which is provided in association with eachskirt section 40, constitute components of a mechanism 71 forreleasably' constraining the lower margins ofinner skirt sheets 41 frommoving outto the sheet inner face, i.e., the face of the skirt sheetwhich opens toward outer skirt sheet 42. As shown best in FIG. 4, atleast a pair of locating assemblies 72 are associated with'each tie-downbar, as are a plurality of latch assemblies 73 and the connectors'67 forthe drawlines 61 associated with each skirt section. The positioningassemblies, latch assemblies, and drawline connectors are spaced atdesired intervals along the length of the tie-down bar.

FIG. 3, illustrates a different energy transfer mechanism 19 from thatshown in FIG. 1. Mechanism 19' takes the form of a hot gas plenumchamber 75 defined peripherally around the interior of body 11 toextend, in cooperation with each side of the'body, from adjacent thebilge 21 to the desired elevation on the side wall of the body. Chamber75 is defined by a suitable enclosure having a top closure portion 76and a side closure portion'77 cooperating with each other and with theinterior of the body side walls and bottom, respectively. I-Iot gas,such as air warmed by the exhaust of diesel engine 30, for example, maybe circulated through chamber 75 for the transfer of thermal energythrough the adjacent side walls and bottom of the vehicle for enablingthe vehicle to maintain a fixed position within a laterally rnoving icesheet during use of the vehicle with the skirt sections in theirretracted position, as'described above.

As shown best in FIGS. 4 and 5, each of the several positioningassemblies 72 includes a conical projection 79 secured to the outer faceof corresponding tie-down bar 70; the outer face of the tie-down bar isthe face of the tie-down bar which opens toward the inner face of innerskirt sheet 41. Projection 79 extends through a suitable opening 80provided in the adjacent inner skir't sheet to cooperate with a matingtapered opening 81 formed in body side wall 15 adjacent bilge 21. Eachopening 81 preferably is a component of a seat for projection 79, suchseat further being defined by a conical inner wall 82 of an inner boss83 provided at the lower end of a tube 84. The lower end of the tube issealed in watertight relation to the inner surface of body wall 15 aboutopening 81. As shown in FIG. 3, each tube 84 traverses hot gas chamber75 to an inner end 85 which opens through the vertical closure portion77 of chamber 75. Each tube 84, one of which is provided in eachpositioning assembly 72, serves as a-passageway for a cable 86 whichextends from a connection at one of its ends to the correspondingconical projection I 79, through tube 84 and to a winch 87 disposedwithin the interior of vehicle body 11. A separate winch 87 may beprovided for'each cable 86 or, preferably, a single winch may beprovided for all of the cables associated with a particular skirtsection 40. FIG. 3 illustrates that the preferred location of winches 87is on the vertical closure wall 77 for hot gas chamber 75. To assurethat each cable86 passes through substantially the center of the innerend of the corresponding tube 84, a guide roller 88 is provided at asuitable location adjacent the inner end of each tube 84, as shown bestin FIG. 3.

The several positioningassemblies associated with each skirt section areprovided to assure that, as the skirt section is moved from itsretracted to its deployed position, those portions of the several latchassemblies which are carried by the tie-down bar of the skirt sectionare appropriately positioned relative to vehicle body 11 for cooperationwith those portions of the latch assemblies which are mounted to body11.

Each latch assembly 73, as shown in FIG. 6, includes a block 90 affixedto the outer face of tiedown bar 70. An internally threaded hole 91 isformed through the tie-down bar and .into block 90 as a component ofeach latch assembly. An opening 92 is provided through the inner skirtsheet 41 in alignment with each hole 91. A reversible electric motor 93,having a rotatable and reciprocal shaft 94, is affixed to the innersurfaces of body side wall 15 adjacent bilge 21 as a further componentof each latch assembly 73. Each motor is so positioned within body 11thatwhen corresponding tiedown bar 70 has been properly positionedrelative to the vehicle body by operation of positioning assemblies72,.the shaft of each motor is coaxially aligned with the correspondinginternally threaded hole 91. The outer end of motor shaft is externallythreaded, as at 95, to mate with the threads of hole 91. To enablecooperation of the motor shaft with hole 91, an opening 96 is providedthrough the vehicle body coaxially of each motor shaft. Preferably, theconnection of each motor to the inner surfaces of body side wall 15is awatertight connection about opening 96. It is also preferred that eachmotor be disposed within a watertight housing 97 I with the powerconductors 98 for the motor being passed through the housing via asuitable watertight seal assembly 99.

Preferably, each motor shaft 94 is splined within its motor armature sothat rotation of the motor armature is transmitted to the motor shaft.The connection of each motor shaft to the armature also includes anaxial drive mechanism which is effective to move the shaft axially ofthe armature in the absence of any substantial resistance to rotation ofthe motor shaft. These connections of the motor shaft to the motorarmature are ar ranged so that the motor shaft moves linearly into andthrough opening 96 at the same time as the shaft is rotated in adirection to produce threading engagement between the external thread 95on the shaft and the internal threads of hole 91.,Conversely, when themotor 93 is operated in the opposite direction, threads 95 aredisengaged from hole 91 and the motor shaft is moved away from backupbar 70 to its retracted position, shown in broken lines in FIG.- 6.

From the foregoing description, it is apparent that the constrainingmechanism 71 associated with each skirt section 40 is composed ofpositioning assemblies 72 and latch assemblies 73.

. Assume that a given skirt section 40 and its plenum section are intheir furled and retracted positions shown in broken linesin FIG. 3; inorder for the skirt section to be so disposed, it is apparent thatcables 86 associated with that skirt section must be paid out fromcorresponding winches 87, and this is represented by a broken line inFIG. 3. Assume further that it is desired to dispose the skirt sectionin its deployed position for :10 air cushion mode operation of vehicle10. Plenum section 33 is moved into its deployed position and skirtassembly 40 is unfurled as air is supplied to the interior of the plenumsection from blower 25 in the manner described above. As the plenumsection is moved to its deployed position, and as the skirt section isunfurled from the plenum section during this process, cables 86 for thatskirt section are reeled in via winches 87 so that, as the skirtcompletely unfurls, conical projections 79 of the several positioningassemblies 72 are moved into snug mating engagement with their seats, asshown in FIG. 5. This reeling in of cables86 during the unfurling ofskirt section 40 may be relied upon to assist in the unfurling processsuch that the commencement of the supply of pressurized air to the skirtsection can be delayed until the skirt section is completely unfurledand latched down to the vehicle body. In any event, snug mating of eachof the several projections 79 carried by the tie-down bar of the skirtsection is assured by the tensioning on cables 86 from winch 87, andsuch positioning assures the proper coaxial alignment of internallythreaded holes 91 of the same tie-down bar with the several motors 93 ofthe associated latch assemblies. Once the tie-down barhas been properlypositioned relative to the vehicle body as shown in FIG 5, the motors 93of the respective latch assemblies are operated to cause the motorshafts to be advanced outwardly from the vehicle body toward thetie-down bar. Such operation of the motors causes the externallythreaded outer end of each motor shaft to thread itself into thecorresponding internally threaded hole 91. The torque imposed upon themotor shafts during this process is sufficient to assure that the lowermargin 47 of inner skirt sheet 41 is securely clamped between thetie-down bar and the vehicle body as each motor shaft reaches the limitof its axial movement outwardly of the vehicle body. When all of the.skirt sections have been deployed and v releasably connected adjacenttheir lower margins to the vehicle body in the manner described above,the vehicle maybe operated in its air cushion mode during which theskirt assembly maintains its proper position relative to the vehiclebody.

It will be apparent that, to enable retraction of the skirt and plenumsections, and to enable furling of the skirt sections on the retractedplenum sections, all that is necessary is that motors 93 for therespective skirt sections be operated in reverse to cause motor shafts94 to unscrewfrom internally threaded holes 91 and that winches 87 beoperatedto pay out cables 86 as winches 66 are operated to reel indrawlines6 1. The disposition of a portion of cables 86 adjacent theexterior surfaces of body 11 when the several skirt sections are intheir retracted and furled positions does not provide any significantimpediment to the operation of the energy transfer mechanisms carried byvehicle 10. Thus, the energy transfer mechanisms carried by the vehiclemay be operated effectively to permit the vehicle to maintain a desiredposition over a fixed submerged location for the purposes described inthe previously mentioned copending application.

When the skirt assembly and plenum structure are fully retractedrelative to the vehicle body to permit the vehicle to be operated asdescribed in the copending application, the lower ends of cable tubes 84are-diswinches 87 and cable guide rollers 88 be mounted within anairtight housing 101 to which compressed air is applied via a suitableduct 102 at a pressure some what greater than-the hydrostatic pressureof water at the lower end of the tube. In this manner, air is caused toleak from the inside of the vehicle outwardly, rather than to allowwater to leak into the interior of the vehicle. As shown in FIG. 5,leakage of air out of the vehicle, or the leakage of water into thevehicle via tubes 84 is further inhibited by a suitable seal assembly103 at the inner end of each tube 84 and through which the correspondingcable 86 passes. A-suitable seal assembly may be a soft rubber blockhaving a hole therethrough sized for snug cooperation with the outerdiameter of cable 86. i

It is desired that the hinge axis 51 by which each plenum section 33 or33' is movably connected to vehicle body 11 be disposed outboard of thebody from the position at which the lower edge 48 of skirt outer sheet42 is disposed when the plenum and skirt sections are in their fullydeployed positions; this condition is shown in FIG. 3. Accordingly, whenvehicle 10 is operated in its air cushion mode, the bottom 13 of thevehicle body is disposed above support surface 24 by a distance H whichis thenormal hover height of the vehicle. The precise value of hoverheight H will be dependent upon the effective weight of the vehicle, thepressure of the air supplied to the space between the vehicle andsupport surface 24 within the confines of skirt 23, and the area of body11 upon which such air pressure may act vertically. The inboarddisposition of outer sheet lower edge 48 from hinge axis 51, however, incombination with the movability of plenum sections 33 relative to thevehicle body, provides vehicle 10 with the capability to increase hoverheight H by an' amount A. Distance A is equal to the height of the chorddefined by the intersection of support surface 24 (assuming the vehicleis operated at its normal hover height H) with the are 69 (having radiusR from hinge axis 51) swept by the bottom edge of outer sheet 42 abouthinge axis 51 as the plenum section is hinged relative to the vehiclebody during air cushion mode operation of the vehicle. In other words,if the depth D is the vertical distance of vehicle bottom 13 below hingeaxis 51, then R D+H+A.

It was noted above that the several plenum sections cooperate intimatelywith each other in their fully deployed state; and that the severalskirt sections also cooperate intimately with each other when the plenumsections are fully deployed. This intimate cooperation is maintainedthrough the initial stages of movement of the plenum sections from theirfully deployed to their retracted positions due principally to theflexibility and limited expansibility of the skirt sections. That is,the skirt sections are so defined that they tend to balloon somewhatfrom their normal operative configurations in which the end and innersheets of each skirt section are constrained by engagement with the sidewalls of the vehicle body or with the end sheets or inner sheets ofadjacent skirt sections. It is apparent, therefore, that one or all ofthe plenum sections may be hinged about axes 51, through the initialportions of their total hingeable movement relative to the vehicle body,and still maintain an effective circumferential seal on the pressurizedspace provided between support surface 24 and the vehicle during aircushion mode operation of the vehicle. Accordingly, the maximum hoverheight capable of being realized in vehicle 10 is normal hover 1 heightH plus additional, height increment AQThis variability in the hoverheight of vehicle 10 is achieved at constant air pressure under thevehicle. Since the plenum sections are separately movable, the vehiclemay maintain an even keel while moving over a slope, or it may step upover an obstruction on surface 24.

Those skilled in the art pertinent to air cushion vehicles and thedesign of skirts for such vehicles will appreciate that vehicle 10 maybegiven some inhcrcnt pitch and roll stabilization properties byarranging skirt purposes of increasing theeffective hover height of thevehicle above surface 24, this increase in effective hover height isattained at the expense of a partial sacrifice in the pitch and rollcompensating characteristics of the vehicle. This is true because suchmovement of the plenum sections about hinge axes 51 produces an increasein the value of the included angle between support surface 24 andthe'outer surfaces of the outer sheets of the skirt sections.

constraining mechanisms 71 are operable to provid the necessaryconstraint of the lower margins of inner skirt sheets 41 from undesiredmovement away from body 11 during movement of the plenum and skirtsections through the initial portion of their path from de ployed toretracted states. That is, the constraining mechaniss can be used tomaintain proper deployment of the skirt sections as the skirt sectionsare moved to increase the hover height of the vehicle. If an increase inhover height is desired, over and above hover height H, latch assemblies73 are operated to disengage motor shafts 94 from tie-down bars duringair cushion interiors communicate with each other when the sev-' eralsections are in their deployed state. Where the plenum sectionsintercommunicate, suitable seals (not shown) are provided for thesections to seal the plenums to each other at their ends when deployed,but the seals must also permit the several sections to be hinged intotheir retracted positions. If the seals are arranged to maintainpressure within the plenum sections during the initial portions ofretraction of the plenum sectionsfrom their deployed positions,,then theabovedescribed hover height variability will be attained.

The invention has been described above with reference to a singleillustrative but presently preferred embodiment of the invention. Itwill be appreciated that structural arrangements other than thosedescribed above may be used to practice the advances made by thisinvention without departing from the scope of the invention. Forexample, the use of a hinge connection between the skirt sections andthe vehicle body is only one. type of connection which may be used tomount the skirt sections for movement between deployed and retractedpositions. Accordingly, the foregoing description should not be regardedas restricting the scope of the invention.

What is claimed is: r

1. In an air cushion vehicle including a body having a gunwale and sidesurfaces extending downwardly from the gunwale to the bottom of thebody, a flexible skirt disposed peripherally of the body and extendingadjacent the body side surfaces for enclosing a space below the body,and means for supplying air at superatmospheric pressure to the spacefor supporting the body above an adjacent support surface, theimprovement comprising a plurality of skirt sections arranged tocooperate with each other to define the skirt, and

means mounting each skirt section to the body for movement of thesections between a deployed position below the gunwale in which eachsection cooperates with adjacent sections so disposed to enclose saidspace and a retracted position in which the skirt sections are disposedsubstantially adjacent the gunwale and the body side surfaces areexposed.

2. Apparatus according to claim 1 including support means for each skirtsection to which the skirt section is essentially permanently mounted,and wherein the means mounting each skirt section to the body includesmeans mounting the support means to the body for movement relative tothe body between positions corresponding to'the deployed and retractedpositions of the skirt sections.

3. Apparatus according to claim 2 wherein the support means comprises apart of the air supplying means.

4. Apparatus according to claim 1 wherein the air supplying meansincludes plenum means around the body substantially at the gunwale, andwherein the skirt sections are arranged to cooperate with the plenummeans in their deployed position for supply of air via the skirtsections to the space.

5. Apparatus according to claim 4 wherein the plenum means includes aplenum section for each skirt section, and including means mounting eachplenum section to the body for movement with the corresponding skirtsection between its deployed and retracted po-' sitions. 5

6. Apparatus according to claim 5 wherein the air supplying means isarranged for air flow connection to the plenum structure throughoutmovement of, the plenum sections between the deployed and retractedpositions of the corresponding skirt sections.

7. Apparatus according to claim 5 wherein the air supplying meansisarranged for parallel flow of air to the skirt sections via therespective plenum sections.

8. Apparatus according to claim 7 wherein each skirt section is arrangedto receive air at superatmospheric' pressure only from the correspondingplenum section. 9. Apparatus according to claim 5 wherein each skirt l4section is connectedat its upper extent to the corresponding plenumsection for movement with the corre sponding plenum section relative tothe vehicle body. I

10. Apparatus according to claim 5 wherein the plenum section mountingmeans comprises hinge means mounting the plenum sections to the vehiclebody.

11. Apparatus according to claim 10 wherein each skirt section is soarranged that when the correspond ing plenum section is in its deployedposition the lower margin of the corresponding skirt section is disposedinwardly of the vehicle from the hinge axis for the plenum section.

12. Apparatus according to claim 1 wherein the skirt sections and theair supplying means are cooperatively arranged for operation thereoffor. air cushion support of the vehicle throughout a selected initialportion of the movement of the skirt sections from their deployedposition 'to their retracted position.

13. Apparatus according to claim 12 wherein the skirt sections arearranged for increasing the effective hover height of the vehicle inresponse to movement of i the skirt sections through said selectedinitial portion of movement from their deployed position during aircushion mode operation of the vehicle.

14. Apparatus according to claim 1 wherein the vehicle includes means inassociation with the side surfaces A constraining the skirt section frommovement from the deployed position of the skirt section in response tosuperatmospheric pressure within the space.

17. Apparatus according to claim 16 wherein the constraining meansincludes releasable latching means having components carried by theskirt section and components carried by the vehicle body which cooperate with each other when the skirt section is in a predeterminedposition relative to the body, and means for positioning the skirtsection in its predetermined position relative to the body. i

18. Apparatus according to claim 17 wherein the positioning means isoperable to at least partially control movement of the skirt sectionfrom its retracted position to its deployed position.

19. Apparatus according to'clairn 16 wherein the constraining means isoperable to provide said con straint upon the skirt section both in thedeployed position of the skirt section and during the initial stages ofmovement of the skirtsection from its deployed position toward itsretracted position.

20. Apparatus according to claim 1 including means for at leastpartially furling the skirt sections when the skirt sections are intheir retracted positions.

1. In an air cushion vehicle including a body having a gunwale and sidesurfaces extending downwardly from the gunwAle to the bottom of thebody, a flexible skirt disposed peripherally of the body and extendingadjacent the body side surfaces for enclosing a space below the body,and means for supplying air at superatmospheric pressure to the spacefor supporting the body above an adjacent support surface, theimprovement comprising a plurality of skirt sections arranged tocooperate with each other to define the skirt, and means mounting eachskirt section to the body for movement of the sections between adeployed position below the gunwale in which each section cooperateswith adjacent sections so disposed to enclose said space and a retractedposition in which the skirt sections are disposed substantially adjacentthe gunwale and the body side surfaces are exposed.
 2. Apparatusaccording to claim 1 including support means for each skirt section towhich the skirt section is essentially permanently mounted, and whereinthe means mounting each skirt section to the body includes meansmounting the support means to the body for movement relative to the bodybetween positions corresponding to the deployed and retracted positionsof the skirt sections.
 3. Apparatus according to claim 2 wherein thesupport means comprises a part of the air supplying means.
 4. Apparatusaccording to claim 1 wherein the air supplying means includes plenummeans around the body substantially at the gunwale, and wherein theskirt sections are arranged to cooperate with the plenum means in theirdeployed position for supply of air via the skirt sections to the space.5. Apparatus according to claim 4 wherein the plenum means includes aplenum section for each skirt section, and including means mounting eachplenum section to the body for movement with the corresponding skirtsection between its deployed and retracted positions.
 6. Apparatusaccording to claim 5 wherein the air supplying means is arranged for airflow connection to the plenum structure throughout movement of theplenum sections between the deployed and retracted positions of thecorresponding skirt sections.
 7. Apparatus according to claim 5 whereinthe air supplying means is arranged for parallel flow of air to theskirt sections via the respective plenum sections.
 8. Apparatusaccording to claim 7 wherein each skirt section is arranged to receiveair at superatmospheric pressure only from the corresponding plenumsection.
 9. Apparatus according to claim 5 wherein each skirt section isconnected at its upper extent to the corresponding plenum section formovement with the corresponding plenum section relative to the vehiclebody.
 10. Apparatus according to claim 5 wherein the plenum sectionmounting means comprises hinge means mounting the plenum sections to thevehicle body.
 11. Apparatus according to claim 10 wherein each skirtsection is so arranged that when the corresponding plenum section is inits deployed position the lower margin of the corresponding skirtsection is disposed inwardly of the vehicle from the hinge axis for theplenum section.
 12. Apparatus according to claim 1 wherein the skirtsections and the air supplying means are cooperatively arranged foroperation thereof for air cushion support of the vehicle throughout aselected initial portion of the movement of the skirt sections fromtheir deployed position to their retracted position.
 13. Apparatusaccording to claim 12 wherein the skirt sections are arranged forincreasing the effective hover height of the vehicle in response tomovement of the skirt sections through said selected initial portion ofmovement from their deployed position during air cushion mode operationof the vehicle.
 14. Apparatus according to claim 1 wherein the vehicleincludes means in association with the side surfaces of the body fortransferring energy through the side surfaces from internally of thevehicle.
 15. Apparatus according to claim 14 wherein the energytransferring means is arranged for transferring thermal energy. 16.Apparatus accordIng to claim 1 including means releasably engageablebetween the vehicle body and each skirt section adjacent the bottom ofthe body for constraining the skirt section from movement from thedeployed position of the skirt section in response to superatmosphericpressure within the space.
 17. Apparatus according to claim 16 whereinthe constraining means includes releasable latching means havingcomponents carried by the skirt section and components carried by thevehicle body which cooperate with each other when the skirt section isin a predetermined position relative to the body, and means forpositioning the skirt section in its predetermined position relative tothe body.
 18. Apparatus according to claim 17 wherein the positioningmeans is operable to at least partially control movement of the skirtsection from its retracted position to its deployed position. 19.Apparatus according to claim 16 wherein the constraining means isoperable to provide said constraint upon the skirt section both in thedeployed position of the skirt section and during the initial stages ofmovement of the skirt section from its deployed position toward itsretracted position.
 20. Apparatus according to claim 1 including meansfor at least partially furling the skirt sections when the skirtsections are in their retracted positions.